In the past, various different types of prior art control devices, such as fluid pressure actuated switches for instance, were utilized in an automotive type air conditioning system to control the energization and deenergization of a clutch actuated compressor in such system in response to a low and high value of fluid pressure measured at a preselected point in such system, such as in an accummulator of such system for instance.
In some of these prior art control devices, a snap disc or Belleville type snap washer or the like for instance was utilized to effect the closing and opening of an electrical switch associated therewith in order to control the energization and deenergization of the clutch actuated compressor. The snap disc was translated from a stable configuration to an unstable configuration thereof in response to the occurrence of the aforementioned high value of the fluid pressure measured in the system, and in the unstable configuration, the snap disc drove a switch closed to complete a circuit energizing the clutch actuated compressor. Of course, the snap disc returned from its unstable configuration to its stable configuration in response to the occurrence of the aforementioned low value of the fluid pressure measured in the system, and the return of the snap disc to its stable configuration permitted the switch to open which interrupted the circuit effecting the deenergization of the clutch actuated compressor. Typically, a snap disc will translate between its stable and unstable configuration in response to a force differential which is built-in or preselected during the formation of the snap disc, and in at least some of these prior art control devices, the switch thereof may be adjustably loaded by a spring or the like in order to preselect the value of the force required for the snap disc to close the switch in response to the occurrence of the aforementioned high value of the fluid pressure measured in the system. However, at least one of the disadvantageous or undesirable features of the prior art control devices discussed above is believed to be that the "built-in" force differential of the snap disc is constant and can not be varied or adjusted. Further, it is also believed that the mechanical life of a snap disc may be limited due to the relatively high stresses which occur during the translatory movement of the snap disc between its stable and unstable configurations.